The subject invention relates generally to automotive lamp assemblies. More specifically, the subject invention relates to devices that prevent moisture from accumulating on the interior surfaces of automotive headlamps.
The accumulation of moisture on the interior of automotive headlamps is caused by several different factors and is a common problem in the automotive headlamp industry. For example, ventilation devices are widely used by prior headlamp assemblies to cool the interior of the headlamp and to equalize the pressure between the exterior and interior of the headlamp during operation. While ventilation devices perform these important functions, some of the prior art devices also have the drawback of allowing liquid water to enter the interior of the headlamp during inclement weather conditions, such as rainstorms. To solve this problem, prior art ventilation systems utilize vent patches, vent tubes, and combinations of both to protect against liquid water from directly entering the headlamp. However, these devices have the drawback of not protecting a headlamp assembly against the introduction of water vapor through the ventilation device during the cooling of the headlamp.
Moisture in the form of water vapor can enter a headlamp when the headlamp is turned off and the interior begins to cool (“intake cycle”). As the interior of the headlamp begins to cool, a negative pressure relative to the exterior of the headlamp is created. As used herein, the term “negative pressure condition” means that the pressure in the interior of the headlamp is less than the pressure on the exterior of the headlamp. In order to equalize the pressure, some form of a venting device is placed on the headlamp to allow air from the atmosphere to enter the interior of the headlamp. The air from the atmosphere contains moisture that condenses on the interior of the headlamp once it enters the headlamp assembly.
The condensation on the interior of the headlamp can cause numerous problems. For example, the moisture that condenses on the interior of the headlamp may cause degradation of the materials comprising the headlamp assembly and lead to the complete failure of the headlamp. Moreover, the condensation can create an undesirable aesthetic appearance, diminish the intensity of the light emitted from the headlamp and alter the direction of the light emitted from the headlamp. Thus, the condensation can cause the light emitted from the headlamp to fall outside of the governmental regulations for headlamps.
One attempt to prevent water vapor from entering the headlamp and condensing on the interior of the headlamps is the use of venting devices which contain a desiccant or a drying agent. However, a desiccant or drying agent alone becomes ineffective at removing the moisture from the air once it becomes saturated with absorbed moisture. Saturation is a common problem with desiccants and drying agents used in ventilation systems due to two factors. First, prior art assemblies do not seal off the desiccant or drying agent from the outside air at any point in time. Thus, the desiccant or drying agent is always exposed to outside air and continually absorbs water from the air during humid conditions.
Second, prior art systems do not allow the desiccant or drying agent to adequately “regenerate.” As used herein, the term “regenerate” means to remove an adequate portion of previously-absorbed moisture from the desiccant or drying agent during the exhaust cycle, thereby conditioning it for the subsequent absorption of additional water vapor (i.e. moisture) during the next intake cycle. The exhaust cycle refers to the period of time that a headlamp assembly is being operated and begins to exhaust heated air from the interior of the headlamp assembly. During the exhaust cycle, the hot exhausting air dries the desiccant or drying agent and allows the desiccant or drying agent to continue to absorb water during further intake cycles and during the period of equilibrium when the headlamp assembly is not in its intake cycle or exhaust cycle. A disadvantage with prior art ventilation devices is that the volume of the exhaust and intake air is not regulated to optimize the process of moisture absorption and removal.
While the prior art does offer some methods of regeneration, none provide for total or even adequate regeneration of the desiccant or drying agent. Due to this problem, the desiccant or drying agent is often in a saturated state and cannot adequately remove water from air that enters into the headlamp. Thus, the introduction of moisture to the interior of a headlamp is still a problem that plagues the art. Accordingly, it is desired to provide a, system that results in a continually condensation free headlamp interior.